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Flashcards in microscope histo Deck (72)
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1

an instrument composed of several lenses used in magnifying objects too small to be seen by the naked eye

microscope

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inventor of the microscope

zacharias jansen

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improved the microscope; Father of Microbiology

Anton van Leeuwenhoek –

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USES VISIBLE LIGHT FOR ILLUMINATION

light microscope

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– uses visible light as light source; shows internal structure and outline of the transparent sheath

BRIGHT FIELD MICROSCOPE

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- examination of live microorganisms not seen under an ordinary light microscope
- possess opaque disks
- suitable for structures that cannot be stained or easily distorted
- useful for detection of Spirochetes

DARKFIELD MICROSCOPE

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- used to facilitate detailed examination of the internal structures of living specimens
-especially for transparent objects

PHASE CONTRAST MICROSCOPE

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- Principle in phase contrast microscope

Light Changes its speed when passing through cellular and extracellular structures with different refractive indices

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- produces images with a 3-D aspect as compared to phase-contrast microscopes
- objects appear bright against a dark background

DIFFERENTIAL INTERFERENCE MICROSCOPE

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two types of DIFFERENTIAL INTERFERENCE MICROSCOPE

: Hoffman (modulation contrast)
Nomarski (differential contrast)

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-Uses a strong UV Light Source and special filters that select rays of different wavelength
- Use of fluorescent compounds such as Acridine Orange, Rhodamine

FLUORESCENCE MICROSCOPY

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Principle of FLUORESCENCE MICROSCOPY

: Substances are exposed to light (radiation) at a wavelength, these emit light with a longer wavelength which is visible

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- more advantageous than regular bright field microscopes
-Uses small point of high intensity light (laser) and a pinhole aperture

CONFOCAL MICROSCOPE

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- Advantage of CONFOCAL MICROSCOPE

avoids stray light; produces more resolution

15

- used for viewing highly organized molecules (crystals and lipids, cellulose, collagen, microtubules, microfilaments)
- uses the principle of polarization wherein light can be rotated in one direction or another (“birefringence”)

POLARIZING MICROSCOPE

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Uses beams of electrons to produce a magnified image
Has greater resolving power as compared to light microscopes; Has higher resolution (1000fold increase)

electron microscopy

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-Allows magnifications of up to 400,000 times
- Requires very thin sections (40-90nm)
-Freeze Fracture Techniques are usually combined in TEM
-Used to Examine Viruses or Internal UltraStructures of cells
-Structures appear as black/gray or white

TEM

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- Studies the surface features of cells and viruses
- Provides a 3-D image of the surface

SCANNING ELECTRON MICROSCOPY

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It is particularly useful for evidence not requiring very high magnification (10x–125x).

Its large working distance makes it quite applicable for the microscopic examination of big, bulky items.

Stereo/Dissecting Microscopes

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: ability of the lenses to distinguish fine detail and structure
refers to the ability of the lenses to distinguish between two points a specified distance apart


Resolution

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------ wavelength: the ------ the resolution

shorter; greater

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resolution is dependent on the ------ used

Dependent on the Objective Used

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ability of the microscope to distinguish/separate 2 points distinctly

Resolving Power:

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a measure of the light bending ability of a medium (substances through which light passes)

Refractive Index

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distance between the objective and object being focused (slide)

Working distance:

26

Magnification: Formula

magnification of ocular x objective magnification

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function of the wavelength and characteristic of the lenses
gives the idea of how much light can enter the objective
Measures light gathering ability of the microscope

Numerical Aperture:

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only slight adjustment is needed to focus the object being studied when the objective is shifted from one objective to another.

Parfocal:

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used to preserve the direction of light rays at the highest magnification.

Immersion Oil:

30

See to it that the________objective is in position when the microscope is not in use

LPO

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